We propose a novel approach for the broadband generation of orbital angular momentum (OAM) carrying beams based on the Archimedean spiral. The mechanism behind the antenna is theoretically analyzed and further validated by numerical simulation and physical measurement. The results show that the spiral-based antenna is able to reliably generate the OAM carrying beams in an ultra-wide frequency band. Of particular interest is the fact that the mode number of radiated beams is reconfigurable with a change in operating frequency. Prototypes of a single-arm spiral antenna (SASA), a multi-arm spiral antenna (MASA), and a compact multi-arm spiral antenna (CMASA) are investigated and demonstrated to support our arguments. The proposed approach provides an effective and competitive way to generate OAM carrying beams in radio and microwave bands, which may have potential in wireless communication applications due to its characteristics of simplicity, broadband capacity and reconfiguration opportunities.
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